1. Field of the Invention
The present invention relates to an image forming apparatus, in particular, one employing an indirect transfer method.
This application is based on Patent Application No. Hei 11-15870 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In the transfer and fixing section of conventional image forming apparatuses, it has been difficult to select a material suitable for the surface layer of the primary or first transfer roller because ozone deterioration of a silicone roller may occur, or a portion of the roller where no cross-linking process was performed may gradually run off.
More specifically, the transfer of a toner image is performed using the difference between the critical surface tension values of the surface layer of the belt-like photosensitive body and the surface layer of the primary transfer roller. Therefore, it is necessary that the critical surface tension of the surface of the primary transfer roller is always higher than that of the belt-like photosensitive body. Simultaneously, in order to easily detach the paper subjected to a secondary transfer and fixing process, it is necessary to keep the adhesive power between the surface of the primary transfer roller and the toner image lower than the adhesive power between the paper and the toner image. Therefore, the upper limit of the critical surface tension of the surface of the primary transfer roller must be strictly defined. It has been difficult to satisfy such a requirement by selecting a suitable material.